Photo-eye protection
The beam detects an obstruction before the descending door makes contact. Sensors must be compatible with the operator; “universal-looking” hardware is not proof of compatibility. [1]
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Garage Door Knowledge Center
Garage door safety sensors
Understand the photo eyes, describe a closing problem, and know what a proper safety check includes.
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Manufacturer references and photo credits are listed in this guide.
A homeowner’s guide
A closing problem deserves its own diagnosis.
Photo-eye sensors use a light beam to detect an obstruction near the opening. A closing fault can involve that beam, its wiring, or another part of the door and opener system. [1]
Start with the behavior you already noticed: refuses to close, starts down and reverses, or reverses after reaching the floor. These are useful distinctions for a service request.
Do not bypass, relocate or disconnect the sensors to make the door close. If the door is crooked, straining, or has spring or cable damage, stop using it and arrange an inspection.
01
Recognize the situation
Which closing symptom matches?
Describe what happened without repeating a movement that appears unsafe.
Refuses to start down
Mention any flashing light or error message, and which control you used.
Starts down, then reverses
Note where it reversed and whether something was already visible near the opening.
Reaches the floor, then returns
Report that sequence separately. A reversal at the floor does not by itself prove a photo-eye fault.
A closer look
Look low on each side.
A typical residential photo-eye pair faces across the opening near floor level. DASMA says these sensors should not be mounted higher than six inches above the floor. [2]
The indicator visible here does not establish alignment, correct mounting or a working safety system.
02
Understand the system
Beam detection and contact reversal.
These functions answer different questions. An illuminated sensor is only one observation.
Contact reversal
The operator also needs the reversal checks specified for its model. Ask the technician to verify the required safety functions after repair. Never use a person or pet as a test object. [4]
03
Make an informed choice
Write down the light pattern and model.
If the indicators are visible from a safe position, note their colors, whether they are steady or flashing, and any repeat pattern. Include the opener model if you have it in a manual or previous invoice.
For example, Genie publishes a Safe-T-Beam diagnostic chart for its systems. Those combinations should not be applied to another brand or a different sensor arrangement. Use the matching manufacturer guidance. [3]
04
From information to action
Choose the next step.
01 / NEXT STEP
Identify the system
Provide the opener model and observed closing behavior, without buying sensors first.
02 / NEXT STEP
Find the cause
Ask whether the fault is the beam path, a component, wiring, or another door issue.
03 / NEXT STEP
Verify protection
Confirm that the repaired system receives the manufacturer’s operation and safety checks.
Ready to review your repair options?
Use the Repair Wizard for the currently listed services, review your quote, and continue to booking. If the cause is uncertain, request an estimate from Wesley.
From our customer stories
Real jobs that explain this topic
The installation record below shows where sensor alignment fits into an opener service visit.
Sensor alignment during two opener installations in Marysville
- Problem or project need
- Renato’s project involved installing two garage door openers, one for each door.
- Work performed
- The installation record includes setting travel and force limits, aligning the safety sensors, checking each door’s movement and testing both completed systems.
- How this connects to the guide
- This example shows sensor checks as part of a complete opener installation. It is not a record of a sensor fault, and it does not mean that every closing problem comes from the sensors.
Renato’s review highlights punctual service and Wesley’s knowledge of the work.
Summaries use the work descriptions and customer feedback on the linked project pages. Each job has its own scope; your repair and price may differ.
05
Quick answers
Common questions
Do both sensor lights have to be green?
There is no universal color rule. Read the indicator chart for the exact opener and sensors; some systems use different colors on each side. [3]
Why does the door close only while I hold the wall button?
On some openers, the manufacturer allows temporary closing with constant pressure on the wired wall control when the safety-eye system prevents normal closing. This is model-specific: check your opener’s manual. Keep the entire doorway in view and clear of people, pets and objects throughout closing. Do not disconnect or defeat the sensors, and stop if the door binds or appears damaged.
This symptom points to a safety-eye issue to investigate, such as obstruction, alignment or wiring; it does not prove the sensors themselves have failed. Arrange service to restore normal operation. Chamberlain’s sensor guidance and Genie’s safety-system guidance describe this feature.
Are replacement sensors interchangeable?
Use devices approved for the operator. Compatibility is a system requirement, not something established by a matching plug or housing. [1]
Why does the door reverse only sometimes?
Describe the timing, any visible obstruction and changes around the opening. An intermittent symptom still needs its cause identified; it does not automatically mean the motor must be replaced.
Where do I start if I cannot identify the fault?
Use the diagnosis hub to organize the symptom, or request an estimate directly. If the required service is already known, the Repair Wizard provides the pricing and booking route.
Read the source material
Guidance you can check.
These primary references support the technical explanations. Use the instructions for your exact door and opener when a procedure or product requirement depends on the model.
- [1] DASMA · TDS 363Photoelectric sensor evaluationLight-beam sensing and compatibility with the operator.
- [2] DASMA · TDS 369Automated residential garage door systemsSensor placement and the complete automated door system.
- [3] The Genie CompanySafe-T-Beam diagnostic guideModel-specific indicator patterns; not a universal color chart.
- [4] DASMAAutomatic opener safety and maintenanceRoutine inspection and separate safety-function checks.
Help from Trinitron Garage Doors
Understand the repair.
Then book with confidence.
Work with a local, veteran-owned garage door business serving Puget Sound. Review your repair options online or talk them through with Wesley.
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